The original idea of coupling implied that there was actually some undefined force that kept two dominant alleles from two different genes together during the process of gamete formation.  Thus the gamete containing the dominant alleles A & B (and its counterpart gamete ab) deviated from independent assortment.  This couplingcould be partial or complete.  In 1911 Bateson and Punnett discovered gametes with one dominant and one recessive allele (i.e., Ab & aB).  These they called repulsion gametes.The mysterious force turned out to be the close proximity of two genes on the same chromosome.  The terms coupling and repulsion only make sense if the two genes show complete dominance.  Nevertheless, the terms live on in genetics textbooks and classes despite their limited usefulness.When I use the terms coupling and repulsion in this tool box  I refer to the specific case of two autosomal genes A and B which show complete dominance.Coupling refers to the case where  dominant alleles are on the same homologue chromosome and both recessive alleles are on the other homologue chromosome.  Thus, the parental gametes are AB and ab.  Some authors call this cis.Repulsion refers to the case where  each homologous chromosome has one dominant and one recessive allele from the two genes. Thus, the parental gametes are Ab and Ab.  Some authors call this trans.